The technical meaning of "an element of speech" first arises in discussion of grammar (particularly Latin grammar), as in the prologue to Wyclif's Bible (ca. 1400):

"This word autem, either vero, mai stonde for forsothe, either for but.

Definitions

Depending on the language, words can be difficult to identify or delimit. Dictionaries take upon themselves the task of categorizing a language's lexicon into lemmas. These can be taken as an indication of what constitutes a "word" in the opinion of the authors.

Word boundaries

In spoken language, the distinction of individual words is usually given by rhythm or accent, but short words are often run together. See clitic for phonologically dependent words. Spoken French has some of the features of a polysynthetic language: il y est allé ("He went there") is pronounced /i.ljɛ.ta.le/. As the majority of the world's languages are not written, the scientific determination of word boundaries becomes important.

There are five ways to determine where the word boundaries of spoken language should be placed:Potential pause

A speaker is told to repeat a given sentence slowly, allowing for pauses. The speaker will tend to insert pauses at the word boundaries. However, this method is not foolproof: the speaker could easily break up polysyllabic words.Indivisibility

A speaker is told to say a sentence out loud, and then is told to say the sentence again with extra words added to it. Thus, I have lived in this village for ten years might become I and my family have lived in this little village for about ten or so years. These extra words will tend to be added in the word boundaries of the original sentence. However, some languages have infixes, which are put inside a word. Similarly, some have separable affixes; in the German sentence "Ich komme gut zu Hause an," the noun ankommen is separated.Minimal free forms

This concept was proposed by Leonard Bloomfield. Words are thought of as the smallest meaningful unit of speech that can stand by themselves. This correlates phonemes (units of sound) to lexemes (units of meaning). However, some written words are not minimal free forms, as they make no sense by themselves (for example, the and of).Phonetic boundaries

Some languages have particular rules of pronunciation that make it easy to spot where a word boundary should be. For example, in a language that regularly stresses the last syllable of a word, a word boundary is likely to fall after each stressed syllable. Another example can be seen in a language that has vowel harmony (like Turkish): the vowels within a given word share the same quality, so a word boundary is likely to occur whenever the vowel quality changes. However, not all languages have such convenient phonetic rules, and even those that do present the occasional exceptions.Semantic units

Much like the above mentioned minimal free forms, this method breaks down a sentence into its smallest semantic units. However, language often contains words that have little semantic value (and often play a more grammatical role), or semantic units that are compound words.A further criterion. Pragmatics.

As Plag suggests, the idea of a lexical item being considered a word should also adjust to pragmatic criteria. The word "hello, for example, does not exist outside of the realm of greetings being difficult to assign a meaning out of it. This is a little more complex if we consider "how do you do?": is it a word, a phrase, or an idiom?
In practice, linguists apply a mixture of all these methods to determine the word boundaries of any given sentence. Even with the careful application of these methods, the exact definition of a word is often still very elusive.

There are some words that seem very general but may truly have a technical definition, such as the word "soon," usually meaning within a week.

Logographic scripts use single signs (characters) to express a word. Most de facto existing scripts are however partly logographic, and combine logographic with phonetic signs. The most widespread
logographic script in modern use is the Chinese script. While the Chinese script has some true logographs, the largest class of characters used in modern Chinese (some 90%) are so-called pictophonetic compounds (形声字, Xíngshēngzì). Characters of this sort are composed of two parts: a pictograph, which suggests the general meaning of the character, and a phonetic part, which is derived from a character pronounced in the same way as the word the new character represents. In this sense, the character for most Chinese words consists of a determiner and a syllabogram, similar to the approach used by cuneiform script and Egyptian hieroglyphs.

There is a tendency informed by orthography to identify a single Chinese character as corresponding to a single word in the Chinese language, parallel to the tendency to identify the letters between two space marks as a single word in the English language. In both cases, this leads to the identification of compound members as individual words, while e.g. in German orthography, compound members are not separated by space marks and the tendency is thus to identify the entire compound as a single word. Compare e.g. English capital city with German Hauptstadt and Chinese 首都 (lit. 首都): all three are equivalent compounds, in the English case consisting of "two words" separated by a space mark, in the German case written as a "single word" without space mark, and in the Chinese case consisting of two logographic characters.

Morphology

In synthetic languages, a single word stem (for example, love) may have a number of different forms (for example, loves, loving, and loved). However, these are not usually considered to be different words, but different forms of the same word. In these languages, words may be considered to be constructed from a number of morphemes.
In Indo-European languages in particular, the morphemes distinguished are